Oral Propolis Nanoemulsions Modulate Gut Microbiota to Balance Bone Remodeling for Enhanced Osteoporosis Therapy

The discovery of the bone–gut axis linking bone metabolism to gut microbiota (GM) dysbiosis has revolutionized our understanding of managing degenerative skeletal diseases. Targeting GM regulation has emerged as a promising approach to osteoporosis treatment. Herein, we develop propolis nanoemulsions (PNEs) with enhanced gastrointestinal stability and oral bioavailability for GM-based osteoporosis therapy. Orally administered PNEs exhibit superior antiosteoporosis efficacy in an ovariectomized (OVX) mouse model by modulating the GM structure and metabolites and restoring the intestinal barrier function. Multiomics analysis reveals that a reduction in Streptococcus abundance and an increase in the GM metabolite l -arginine are key factors in osteoporosis management. These changes suppress osteoclast activity and enhance osteoblast function, leading to balanced bone remodeling and, thus, significant antiosteoporotic effects via the gut–bone axis. Our results deepen insights into the intricate relationship between GM and bone remodeling, suggesting a promising strategy that maintains the homeostasis of the GM structure and metabolite for osteoporosis treatment.